<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .box{
            position: relative;
            width: 200px;
            height: 200px;
            margin: 0 auto;
            margin-top: 100px;
            border-radius: 50%;
            background-image: radial-gradient(circle at 10% 20%,yellow,red,green);
        }
        .box::after{
            position: absolute;
            left: 110px;
            bottom: -70px;
            content: '';
            /* display: block; */
            width: 250px;
            height: 100px;
            background-color: rgba(0,0,0,.5);
            border-radius: 50%;
        }
    </style>
</head>
<body>
    <div class="box">

    </div>
</body>
</html>